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Characterization of the channel-pores formed by Bacillus thuringiensis Cry46Ab toxin in planar lipid bilayers

  • Akira Sakakibara
  • So Takebe
  • Toru Ide
  • Tohru HayakawaEmail author
Original Research Paper
  • 13 Downloads

Abstract

Cry46Ab from Bacillus thuringiensis TK-E6 is a new mosquitocidal toxin with aerolysin-type architecture, and has been shown that co-administration of Cry46Ab with other mosquitocidal Cry toxins results in synergistic toxicity against Culex pipiens Coquillett (Diptera: Culicidae) mosquito larvae. Cry46Ab, therefore, is expected to find use in improving the insecticidal activity of B. thuringiensis-based bioinsecticides. In the present study, the mode of action of Cry46Ab was explored by single-channel measurements of Cry46Ab channel-pores. The single-channel conductances of channel-pores formed in planar lipid bilayers by Cry46Ab were determined to be 31.8 ± 2.7 pS in 150 mM NaCl and 24.2 ± 0.7 pS in 150 mM CaCl2. Ion-selectivity measurements revealed that the channel-pores formed by Cry46Ab were cation selective. The permeability ratio of K+ to Cl was approximately 4, and the preferences for cations were K+ > Na+, K+ > Ca2+, and Ca2+ > Na+. A calcein release assay using liposomes suggested that Cry46Ab influences the integrity of membrane vesicles. Formation of cation-selective channel-pores has been observed with other insecticidal Cry toxins that have structures distinct from those of Cry46Ab; the capability of forming such pores may be a property required of insecticidal toxins.

Keywords

Bacillus thuringiensis Cry46Ab toxin Planar lipid bilayer Single-channel analysis Calcein release assay 

Notes

Acknowledgements

C. pipiens eggs were kindly supplied by the Research and Development Laboratory at Dainihon Jochugiku Co., Ltd., Osaka, Japan. This work was supported in part by JSPS KAKENHI Grant number JP18K05675.

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Copyright information

© The Japanese Society of Applied Entomology and Zoology 2019

Authors and Affiliations

  1. 1.Graduate School of Interdisciplinary Science and Engineering in Health SystemsOkayama UniversityOkayamaJapan
  2. 2.Graduate School of Biology-Oriented Science and TechnologyKindai UniversityKinokawaJapan

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